Method of centrifugally casting flanged tubular members



Dec. 27, 1966 F. w. FRUITMAN 3,293,708

METHOD OF CENTRIFUGALLY CASTING FLANGED TUBULAR MEMBERS Filed March 4,1964 FIG-1 28 15 29 FIG-2 FIG-3 INVENTOR.

FRANK W. FRUITMAN ATTORNEYS United States Patent 3 293,708 METHOD OFCENTRIFUGALLY CASTING FLANGED TUBULAR MEMBERS Frank W. F ruitman,Arlington, Va., assignor to The Black Clawson Company, Hamilton, Ohio, acorporation of Ohio Filed Mar. 4, 1964, Ser. No. 349,798 14 Claims. (Cl.22-2005) on the inner surface so that the finished casting has a compactgrain structure free of voids or centerline cavities. Simultaneouslywith the production of these improved grain structures the chemicalmake-up of the molten metal may be changed, fior example, to eliminateor reduce impurities therein.

In addition, this invention has special relation to the method andapparatus disclosed in the copending United States application of WalterE. Rojecki, Serial No. 198,256, filed May 28, 1962, now abandoned, forPaper Machinery, and assigned to same assignce as the presentapplication. In the practice of the invention of the above copendingapplication, a tubular mold or core case is provided with sealed endsand one or more transverse baflles mounted therein with their outerperipheries spaced radially from the inner surface of the mold. Thebafiles thus divide the interior of the mold into at least one flangechamber and a main chamber which are interconnected only by the passagesformed between the baffle and the inner surface of the mold. While themold is being rotated at high speed, a predetermined amount of moltenmetal is poured into the mold, and then the main chamber is connected toa source of gas pressure so that a portion of the molten metal is forcedinto the flange chamber through the passage. The rotation andpressurization of the mold are maintained until the metal solidifies,thus creating a tubular casting having "an integral internal flange foreach flange chamber.

It is an important object of this invention to provide an improved andsimplified apparatus and method for the production of centrifugally casttubular members having internal flanges integrally formed thereon duringthe casting operation, and in particular to provide a method whichachieves in a simplified manner the same end product as the method inthe aforesaid copending application.

Another object of this invention is to provide apparatus for and aprocess of centrifugally casting a tubular member having internalflanges at either end thereof wherein the molten metal is caused to flowfrom a pressure chamber of the mold into one or more flange formingchamber's without the use of apparatus for pressurizing the entire mold,and further to provide such a process which is greatly simplified andthus produces a consistently high quality casting at a substantialsaving in ultimate cost.

A further object of this invention is to provide a process forcentrifugally casting a tubular member wherein the grain structure ofthe metal has substantially fewer voids or cavities between thesolidified grains or dendrites, so that the resulting tubular member issubstantially Patented Dec. 27, 1966 stronger, than similar productsheretofore made by centrifugal casting processes.

A still further object of this invention-is'to provide a process forcentrifugally casting a tubular member in such a manner thatsolidification commences at the outer surface of the tubular member andproceeds radially inwardly to the inner surface, rather than commencingfrom both the inner and outer surfaces of the tubular member as inpresent processes, so that center-line voids or cavities caused byshrinkage of the metal during solidification are eliminated from thecentral area of the tubular member.

Another object of this invention is to provide a process forcentrifugally casting a tubular member which includes the use of a slagmaterial for increasing the compaction of the grain structure as well asfor chemically reacting with the molten metal to change or eliminateundesirable impurities or'chem'ical elements'therein, and particularlyto provide such a process wherein the slag reacts with impurities in themolten cast iron, e.g., to reduce substantially the sulphur content ofthe molten cast iron.

A further object of this invention is to provide a process of theaforesaid type for producing a tubular casting having at least oneintegral internal flange by using a mold which is open at one or bothends for improved cooling of the casting, and particularly to providesuch a process wherein a mass of a fluid material is utilized to createthe head required for forcing the molten metal from the main chamberinto the flange chamber.

Still further objects and advantages of the invention will be apparentfrom the following description, the accompanying drawings and theappended claims.

In the drawings:

FIG. 1 is a sectional view through casting apparatus in accordance withthe invention for performing the method of the invention; 7

FIGS. 2 and 3 illustrate schematically the successive steps of themethod of the invention in conjunction with the apparatus shown in FIG.1; and

FIG. 4 is a schematically sectional view taken essentially along theline 44 of FIG. 3.

Referring to the drawing, wherein a preferred embodiment of theinvention is illustrated, FIG. 1 shows casting apparatus including atubular core case 10 supported on and rotated by the drive rollers 11which engage the drive bands 13 extending circumferentially around theouter surface of the case 10. The core case 10 has end plates 15 and 16secured to'each end thereof by bolts 17 which extend through a suitableaperture in the plates and into the tapped bores 18 in the case 10.Axially extending flanges 19 are provided on the outer periphery of theend plates 15 and 16 for overlying engagement with the ends of the corecase 10 to resist the centrifugal forces acting on the case 10 when itis rotated at high speed.

Each of the end plates 15and 16 has an axially inwardly extending boss20 with a relatively large opening 21 therethrough for connecting theinterior of the case 10 to the atmosphere. The bosses 20 each have anexpendable partition member or baffle 22 mounted on the innermost endthereof by the bolts 23. These partition members are formed of heatresistant material which is preferably frangible to facilitate breakageand removal from the interior of the finished casting, as will beexplained. For example, each of the baflle's 22 may be cast of ceramicmaterial such as baked foundry core sand, a baked mixture of silica sandand calcined gypsum, a baked mixture of silica sand and Portland cementor a baked mixture of .magnesite or other basic refractory material. Inaddition, these baflies can also be made of metal alloys, e.g., steel,depending on the temperature and the particular requirements ofaspecific casting operation. If the presence of the baffles in thefinished casting is not undesirable, the baffle may be constructed of ametal which will be fused to the cast material during the castingoperation and thus form an integral part of the finished product.

The entire inner surface 24 of the core case 10, as well as the'innerend faces 25 of the end plates 15 and 16, are preferably covered with aliner 26 of suitable refractory material so that these components canwithstand the heat encountered when the molten metal is poured into thecore case 10. The liner 26 may be fabricated conventionally of moldingsand for insertion within the core case, or it may be a coating which isapplied to the various surfaces after the core case has been assembled.To aid in the dissipation of heat and moisture from the core case 10, itmay be desirable to perforate the case in accordance with conventionalpractice.

The baffles 22 divide the interior of the core case 10 into a centralpressure chamber 27, and a pair of flange chambers 28 and 29 whichextend between the outer side surfaces 30 of baflles 22 and the innersurface of the liner 26 on surfaces 25 of the adjacent end plates and16, respectively. The chambers 27, 28 and 29 are interconnected solelyby the annular passages 31 between the entire outer periphery of eachbaflle 22 and the inner surface of the liner 26 so that the molten metalwill flow from the central chamber 27 to the flange chambers 28 and 29.The flange chambers 28 and 29 are vented to the atmosphere by aplurality of passages 32 and 33, respectively, so that gases will not betrapped therein to obstruct the flow of metal thereinto. Also thepassages 32 and 33 may be connected to a vacuum which increases thepressure differential between the flange and central chambers 27, 28 and29 to facilitate flow of the molten metal 40 into the flange chambers 28and 29.

An importantfeature of this inventionlies in the improved process forforming a tubular member having integral internal flanges at each endthereof. The process includes pouring a predetermined amount of moltenmetal 40 from the movable ladle device 36 into the central chamber 27 ofthe core case 10 while it is rotating at a predetermined speed, in amanner substantially identical to that described in the aforesaidcopending application. Thus the molten metal is distributed over theentire inner surface 41 of the liner 26 in the case 10 under action ofcentrifugal force, and at this stage of the process the molten metalwill have assumed a configuration similar to that represented in FIG. 2,wherein the grooves 42 are formed by the peripheral edges of the baffles22.

After the pouring of the metal 40 is completed, a fluid or moltenmaterial 45 which has a specific gravity equal to or less than that ofthe molten metal and is substantially inert with respect to the moltenmetal is poured through the spout 46 into the pressure chamber 27. Thismaterial becomes evenly distributed, due to the centrifugal forcesacting thereon, over the inner surface of the metal in the pressurechamber 27, and since it is equal to or lighter in weight than andnon-reactive with the metal 40 there is no tendency of the material 45to mix with the molten metal 40. On the other hand, when the materialhas a specific gravity slightly less than the metal 40, the centrifugalforce acting on this molten metal and material tends to maintainsegregation thereof.

The material 45 has a predetermined volume and height so that the forceor heat acting thereon exerts a force on the molten metal 40 whichforces a portion of the metal through the passages 31 into the flangechambers 28 and 29 to create the flanges 47. The amount of pressure orforce which must be exerted by the molten material 45 during this stepof the process is dependent on the size of the core case 10 and thevarious conditions present in each particular casting operation. Thatis, the size of the casting being made, the specific gravities of themetal 40 and material 45, as well as the height of the material, thespeed of rotation of the core case 10 and the centrifugal force beingexerted on the molten metal 45 are considerations which must beevaluated in determining the volume of the molten material. This forcemust be sufficient to force the molten metal through the annularpassages 31 into the flange chambers 28 and 29 but less than that whichwill reduce the thickness of the metal in the pressure chamber 27 toless than the radial dimension of the passage 31 so that molten material45 will not flow into the flange chambers 28 and 29. Thus if a materialis used which has a specific gravity equal to that of the metal, theinner diameter of the tubular shaped mass of molten material would beequal to the inner diameter of the flanges, and if the specific gravityof the material used is decreased, the inner diameter of the materialbecomes less than the inner diameter of the flanges.

The fluid or molten material 45 used to create the force to cause metalto flow into the flange chamber can be a slag, salt, ceramic or metalliccompound whose specific gravity in the molten state is equal to or lessthan that of the molten metal. The material must not be reactive withthe molten metal, and preferably is frangible in the solid state tofacilitate removal from the casting. Another preferred feature of thematerial 45 which facilitates removal thereof is a coeflicient ofcontraction on cooling which is less than that of the metal 40 so thatthe material separates cleanly from the metal casting during cooling. Ifthe solidification temperature of the fluid material 45 is less than themetal 40, the fluid material 45 may be drained, syphoned or decantedaway from the solidified casting 40 prior to solidifying thereof thusfacilitating removal of the material 45.

By way of example, suitable materials 45 are the metalliC slags Fe O-SiO NaFeCl U O -SiO Pb203SiO2, and LiO-SiO These examples are intendedfor illustration purposes only, and numerous other compounds andmixtures can be used without departing from the scope of the invention.The specific gravity of these materials can be varied by changing theratio of the metallic radical to the silicate radical, for example, inlead slag the volume lead oxide Pb O can be increased or decreased withrespect to the silicate SiO to vary the specific gravity thereof. Alsothe specific gravity can be varied by changing the type of metal oxidein the slag, for example, uranium or lead slags, U O -SiO or Pb O -SiOcan be used for higher specific gravities, whereas lithium slag, LiO-SiOcan be used for a lower specific gravity. As an example, lead silicateslags which are non-reactive with bronze can be used for centrifugallycasting bronze shapes. Application of a vacuum to the vents 32 and 33will permit use of a wider range of lower specific gravity materials orsmaller volume of these materials.

Furthermore, it is within the scope of this invention to use a solid orsemi-solid material in lieu of the molten material 45. Thus a semi-fluidgranulated material which has a density less than the specific gravityof the molten metal and is nonreactive therewith could be utilized toeffect the flow of metal into the flange chambers. Consequently, theterm fluid material 45 as used in this specification is intended toinclude such solid and semisolid materials which are capable ofsubstantially carrying out the functional requirements set forth above.

After the material 45 is added, the rotation of the core case 10 ismaintained until the metal 40 solidifies. To remove the finishedcasting, the end plates 15 and 16 are separated from the core case 10and the finished casting so that the battles 22 remain in the tubularcore case 10. The separation of the baffles 22 from the bosses 20 may beaccomplished by removing the screws 23 or by disintegrating the baffles22 in the areas around these screws. Next the casting is removed axiallyfrom the case 10, and the baflles 22 and material 45 may then be removedby disintegration or machining depending on the type of materials used.

While only a preferred embodiment of the apparatus has been shown andspecifically described, it is within the scope of this invention toprovide numerous other embodiments for carrying out the herein describedinventive method for producing centrifugal castings having one or moreinternal flanges therein. It should be apparent that numerous expedientsmay be utilized by one skilled in the art to mount the baflles used toseparate the flange and pressure chambers.

Similarly, the material used in constructing the bafiles 22 may varywidely depending upon the particular requirements of the specificcasting operations to be carried out thereby. Materials other thanmetals 40 may be cast in accordance with this process so long as theyare capable of changing from a liquid state to a solid state in responseto a change in temperature or chemical action. Thus while the inventionis particularly applicable to the casting of metals, and has been sodescribed, other materials can be similarly cast without departing fromthe scope of the invention.

The illustrated embodiment of the mold produces an integral internalflange on each end of a tubular member, but it is within the scope ofthe invention to place these internal flanges at any point on the innersurface of the tubular member by merely appropriately positioning thebaffles 22 in the molds. For example, if the baflles 22 Were placed inthe central portion of the mold with a space therebetween' suitablyvented to the atmosphere and the metal 40 and material 45 poured intosuitable chambers on the outer sides of these baffles, an internalflange intermediate the ends of the tubular member could be formed. In asimilar manner, the bafiles 22 can be used to form several flangechambers in the mold so that a plurality of flanges can be formed atvarious points on the inner surface of the tubular member.

The casting which is produced by the above described process has ahollow cylindrical body with one or more integral internal flangestherein (see FIG. 3). The metallurgical grain structure of the castingis substantially identical and indistinguishable throughout includingthe junc ture between the flanges 47 and the tubular portion thereof.The slag and other light impurities collect on or near the innermostsurfaces of the casting, that is, on the inner peripheral surface of theflange and on the inner surface of the tubular portion where they can beeasily removed by machining, if desired.

Since no welding operation is required, the casting is not subjected tohigh local temperatures which can cause distortion, and it is producedat a much lower cost since the flange does not have to be producedseparately. It therefore follows that the inner surface of the tubularbody does not require machining prior to welding to remove the slag andother impurities from the area to be welded, as would be required toweld a flange as a separate component to a centrifugally cast body. Alsometals and other materials which are not suitable for welding can beformed easily into a tubular body having internal flanges therein by thepresent process. When a flange having a relatively thick axial dimensionis desired, an appreciably stronger juncture with the body is attainedby this process since a flange of this type could not be welded alongthe entire surface of contact with the body.

Thus a simplified process for forming a tubular member having one ormore internal integral flanges and including all of the advantages ofthe aforesaid copending application has been provided. The castingapparatus need no longer be air tight, and as a result expensive andundesirable rotary connections need not be provided for the end plates.Since both ends of the core case are open, the material 45 and the metal40 can be supplied through the same opening 21 or through opposite ends,as desired. This process produces a casting of consistently high qualitysince the mold need not be pressurized and the ends thereof are openthus facilitating cooling of the casting.

Another important feature of the invention is the improved grainstructure which is produced and, as will be seen, this grain structurecan be produced in centrifugally cast products which do not haveinternal flanges. The molten material 45 acts against the inner surfaceof the liquid metal and thus pressurizes this liquid metal to compressor squeeze the grains or dendrites, together, as these grains aretransformed from a liquid to a semisolid or plastic state and then to asolid state. This action is similar to that which takes place in aforging action, and tends to eliminate the bridging effect of the grainstructure growth so that cavities will not form during solidification ofthe metal.

Since the molten material is still liquid after the metal has solidifiedit acts as a continuous pressure medium during the entire period ofsolidification so that the compression forces are present at all times.The resulting product has fewer cavities or voids and is denser materialwith less sponginess than the normal centrifugal casting. It thus isstronger and is better suited for use in pressure vessels and is lesslikely to fail from fatigue. For example, this greater density willincrease the thermal conductivity of the resulting product so that whenit is used as a drier cylinder for a paper machine, it will be able tocontain higher heating pressures, usually steam.

As is well known, in the conventional centrifugal casting processes themetal initially solidifies adjacent the outer surface and thissolidification proceeds radially inwardly. Shortly thereafter, thesolidification commences on the inner surface and proceeds radiallyoutwardly. As the last portion of the liquid metal betweenthe inner andouter surfaces reaches the solid state, cavities are formed in this areain a random manner since there is no further liquid metal to fill thevoids or cavities which occur as the metal shrinks due tosolidification. These cavities are called centerline cavities andinherently Weaken the end product.

In addition to creating a pressure or force to compact the grainstructure during solidification, the molten material acts as a heat sinkto effect uniform cooling from the outer surface to the inner surface.That is, when a molten material which has a melting point lower thanthat of the metal being cast, the solidification proceeds from the outersurface of the metal radially inwardly to the inner surface thereofsince the molten slag or material maintains the inner surface in aliquid state due to the heat present in the molten material. Since themolten material and metal have substantially different melting points,all of the metal will be solidified prior to the commencement ofsolidification of the slag. As indicated, it may be that this moltenmaterial will be removed prior to solidification.

By using a particular slag or other molten material having a chemicalreactiveness for a particular element in the metal, it is possible toremove or change the chemical makeup of the finished casting. Forexample, when casting cast iron, the removal of sulphur is verydesirable since it tends to make the resulting casting very brittle. Thefollowing example demonstrates the manner in which this sulphur isreduced:

Example Using a small mold, a tubular casting having an average diameterof 8 inches was made by pouring Percent Silicon 2.00 Sulphur 0.088

The slag consisted of barium fluoride and barium chloride in equalmolecular amounts. Although this slag is neutral, barium has an aflinityfor sulphur.

The resulting casting showed that the silicon content was 1.87%, andsulphur 0.031%. Thus 64% of the sulphur in the molten metal was removedas a result of this process. Silicon, phosphorous, or other impuritiescould be similarly removed by using slag materials which have anafiinity for the element which is to be removed. Furthermore, to insurethat the slag absorbs the desired element, rather than the metalabsorbing element from the slag, the slag must be higher on theelectromotive force table than the metal.

Thus it is seen that by selecting proper materials for the slag, theactual composition of the molten metal can be changed as desired. Thechemical action between the slag and molten metal is facilitated by thepressure between the slag and molten metal as created by the centrifugalforce during rotation of the mold. These forces provide an autoclave orbath action which forces the interfaces of these molten bodies togetherunder high pressures and temperatures to improve the efii-ciency andextent to which the chemical reactions take place. This autoclave actionis well known in other and different processes and structures, but hasnever been utilized in the centrifugal casting or tubular members asdisclosed herein.

As indicated above, the slag acts as a heat sink during the castingprocess, and an important advantage thereof is the uniform distributionof heat in the molten metal, as well as the uniform rate of coolingthereof. This creates a homogeneous grain structure throughout thecasting reasonably free of cold or hot spots, and thus has a uniformthermal conductivity. As a result, a better quality paper machine drierroll can be produced thereby. This uniform cooling also prevents theformation of hard and soft spots in the finished casting therebypermitting machining of the casting with greater speed and high quality.

While the methods herein described, and the form of apparatus forcarrying this method into effect, con,- stitute preferred embodiments ofthe invention, it is to be understood that the invention is not limitedto these precise methods and form of apparatus, and that changes may bemade in either without departing from the scope of the invention whichis defined in the appended claims.

What is claimed is:

1. A method of casting a tubular member having at least one internalflange, comprising the steps of pouring a predetermined quantity ofmolten metal into a tubular mold having the interior thereof separatedby baffles into pressure and flange forming chambers interconnected onlyby an annular passage between the outer periphery of the bafiies andinner side walls of said mold, rotating said mold about its axis at aspeed suflicient to cause said molten metal to assume a uniformthickness over the inner side walls of said mold, pouring apredetermined volume of fluid material having a specific gravity notgreater than that of said metal in said pressure chamber to force apredetermined volume of said molten metal from said pressure chamberthrough said passage into said flange forming chamber, correlating saidspeed of rotation and the volume of said material so that the thicknessof said metal on said inner surface is at least equal to the radialdimension of said passage, and maintaining said rotation until saidmetal solidifies so that said metal in said pressure chamber forms atubular member having an integral internal flange thereon in each saidflange forming chamber.

2. A method of casting :a tubular member having at least one internalflange, comprising the steps of pouring a predetermined quantity ofmolten metal into a tubular mold having the interior thereof separatedby bafi les into pressure and flange forming chambers interconnectedonly by an annular passage between the outer periphery of the bafliesand inner side walls of said mold, rotating said mold about its axis ata speed suflicient to cause said molten metal to assume a uniformthickness over the inner side walls of said mold, pouring apredetermined volume of fluid material having a specific gravitysubstantially equal to that of said metal and being non-reactive withsaid metal into said pressure chamber to force an equal volume of saidmolten metal from said pressure chamber through said passage into saidflange forming chamber, correlating the volume of said fluid materialwith the radial dimension of said passage so that the thickness of saidmetal on said inner surface is at least equal to the radial dimension ofsaid passage, and maintaining said rotation until said metal solidifiesso that said metal in said pressure chamber forms a tubular memberhaving an integral internal flange thereon in each said flange formingchamber.

3. A method of casting a tubular member having an internal flange,comprising the steps of placing a predetermined quantity of moltenmaterial into a tubular mold having the interior thereof separated bybaffle means into pressure and flange forming chambers interconnected byan annular passage between the outer periphery of the baffle means andinner side walls of said mold, rotating said mold about the longitudinalaxis at a speed sufficient to cause said molten material to assume auniform thickness over the inner side walls of said mold, then placing aliquid having a specific gravity not greater than that of said metal insaid pressure chamber to force a predetermined amount of said moltenmaterial from said pressure chamber through said passage into saidflange forming chamber, correlating said speed of rotation and thevolume of said material so that the thickness of said material on saidinner surface is at least equal to the radial dimension of said passage,and maintaining said rotation until said material solidifies so thatsaid material forms a tubular member having an integral internal flangein each said flange chamber.

4. A method of casting a tubular member having at least one internalflange, comprising the steps of placing a predetermined quantity ofmolten metal into a mold having an interior chamber separated intopressure and flange forming chambers connected only by an annularpassage adjacent the inner surface of said mold, rotating said mold at aspeed sufficient to cause said molten metal to assume a uniformthickness over the inner surface of said mold, then placing a fluidmaterial having a specific gravity not greater than that of said metaland being nonreactive With said metal in said pressure chamber of saidrotating mold to force a predetermined amount of said molten materialfrom said pressure chamber through said passage into said flange formingchamber, correlating sai-d speed of rotation and the volume of saidmaterial so that the thickness of said metal on said inner surface is atleast equal to the radial dimension of said passage, said materialhaving a coeflicient of contraction during cooling which is greater thanthat of said metal to facilitate removal of said material from thetubular member.

5. A method of casting a tubular member having at least one internalflange, comprising the steps of pouring a predetermined quantity ofmolten metal into a tubular mold having a partition therein separatingthe interior thereof into a central chamber and a flange forming chamberconnected only by an annular passage formed between the outer peripheryof said partition and the inner surface of said mold, rotating said moldat a speed sufficient to cause said molten metal to assume a uniformthickness over the inner surface of said mold, then placing a moltenmaterial having a specific gravity less than that of said molten metalinto said central chamber to force a predetermined amount of said moltenmaterial from said pressure chamber through said passage into saidflange form: ing chamber, and maintaining said rotation until said metalsolidifies so that the metal adjacent said inner surface forms a tubularmember and the metal in said flange forming chamber forms an internalflange on the tubular member.

6. A method of casting a tubular member having at least one internalflange, comprising the steps of pouring a predetermined quantity ofmolten metal into a tubular mold having a partition therein separatingthe interior thereof into a pressure chamber and a flange formingchamber connected only by an annular passage formed between the outerperiphery of said partition and the inner surface of said mold, rotatingsaid mold at a speed sufficient to cause said molten metal to assume auniform thickness over the inner surface of said mold, then placing amolten material having a specific gravity not greater than that of saidmolten metal into said pressure chamber to force a predetermined amountof said molten material from said pressure chamber through said passageinto said flange forming chamber, correlating the speed of rotation withthe weight of said material so that the thickness of said metal on saidinner mold surface is at least equal to the spacing between saidpartition and said surface, and maintaining said rotation until saidmetal and said material solidify so that the metal adjacent said innersurface forms a tubular member and the metal in said flange formingchamber forms an internal flange on the tubular member, said materialbeing of a type which is easily frangible when solidified forfacilitating removal from the tubular member.

7. A method of casting a tubular member having at least one internalflange, comprising the steps of pouring a predetermined quantity ofmolten metal into a tubular mold having a partition therein separatingthe interior thereof into a pressure chamber and a flange formingchamber connected only by an annular passage formed between the outerperiphery of said partition and the inner surface of said mold, rotatingsaid mold at a speed sufficient to cause said molten metal to assume auniform thickness over the inner surface of said mold, then placing amolten material having a specific gravity not greater than that of saidmolten metal into said pressure chamber to force a predetermined amountof said molten material from said pressure chamber through said passageinto said flange forming chamber, and maintaining said rotation untilsaid metal and said material solidify so that the metal adjacent saidinner surface forms a tubular member and the metal in said flangeforming chamber forms an internal flange on said tubular member, saidmaterial having a coeflicient of contraction during cooling which isgreater than that of said metal to separate said material from thetubular member.

8. A method of casting a tubular member having improved grain structurecomprising, the steps of pouring a predetermined quantity of moltenmetal into a tubular mold having a central chamber therein, rotatingsaid mold at a speed suflicient to causesaid molten metal to assume auniform thickness over the inner surface of said mold, then placing amolten material having a melting point lower and a specific gravity lessthan that of said molten metal into said central chamber to compact saidmolten metal during solidification, said material acting as a heat sinkto cause solidification of said metal to proceed from the outer surfaceof said metal radially inwardly to the inner surface thereof toeliminate centerline cavities in the finished casting, said heat sinkeffecting substantially uniform distribution of heat in said metal anduniform cooling thereof to create a more homogeneous grain structurethroughout the tubular member, and maintaining said rotation until saidmetal solidifies so that the metal forms a tubular member having animproved compacted grain structure.

9. A method of casting a tubular member having improved strength and adenser grain structure comprising, the steps of pouring a predeterminedquantity of molten metal into a tubular mold having a central chambertherein, rotating said mold at a speed sufficient to cause said moltenmetal to assume a uniform thickness over the inner surface of said mold,then placing a molten slag having a melting point lower and a specificgravity less than that of said molten metal into said central chamber tocompact said molten metal during solidification to force the sameagainst the walls of said mold for greater precision in the outerdimensions of the tubular member so that less machining is required,said slag acting as a heat sink to cause solidification to proceedprogressively from the outer surface of said metal radially inwardly tothe inner surface thereof to compact said metal and form a denserfinished casting, and maintaining said rotation until at least saidmetal solidifies so that said metal forms a tubular member.

10. A method of casting a tubular member comprising, the steps ofpouring a predetermined quantity of molten metal into a tubular moldhaving a central chamber, rotating said mold at a speed sufficient tocause said molten metal to assume a uniform thickness over the innersurface of said mold, then placing a molten material having a specificgravity less than that of said molten metal into said central chamber,said material being chemically reactive with certain elements in saidmetal to change the chemical content thereof, said rotation of said moldcreating a pressure between the interfaces of said material and moltenmetal for cooperation with the temperature of said molten metal to raisethe efficiency of the reaction between said material and said metal, andmaintaining said rotation until said metal solidifies so that the metalforms a tubular member having a composition different from the moltenmetal as poured into said chamber.

11. A method of casting a tubular member comprising, the steps ofpouring a predetermined quantity of molten metal having impuritiestherein into a tubular mold having a central chamber, rotating said moldat a speed suflicient to cause said molten metal to assume a uniformthickness over the inner surface of said mold, then placing a moltenmaterial having a specific gravity less than that of said molten metalinto said central chamber, said material being chemically reactive withsaid impurities and being higher in the electromotive series than saidmetal so said impurities combine with said slag, said rotation of saidmold creating a pressure between the interfaces of said material andmolten metal for cooperation with the temperature of said molten metalto raise the efliciency of the reaction between said material and metal,and maintaining said rotation until said metal solidifies so that themetal forms a tubular member having a composition different from themolten metal as poured into said chamber.

12. A method of casting a tubular member comprising, the steps ofpouring a predetermined quantity of molten metal having impuritiestherein into a tubular mold having a central chamber, rotating said moldat a speed sufiicient to cause said molten metal to assume a uniformthickness over the inner surface of said mold, then placing a moltenmaterial having a specific gravity less than that of said molten metalinto said central chamber, said rotation of said mold being suflicientto cause said material to assume a uniform thickness on the innersurface of said metal, said material being chemically reactive with saidimpurities and being higher in the electromotive series than said metalso said impurities combine with said slag, maintaining said rotationuntil said metal solidifies so that the metal forms a tubular memberhaving a composition different from the molten metal as poured into saidchamber, and removing said material with said impurities therein fromsaid metal to thus produce a tubular member of increased quality.

13. A method of casting a tubular member comprising, the steps ofpouring a predetermined quantity of molten cast iron having sulfurimpurities therein into a tubular mold having a central chamber,rotating said mold at a speed suflicient to cause said molten metal toassume a uniform thickness over the inner surface of said mold, thenplacing a molten barium salt slag material having a specific gravityless than that of said molten metal into said central chamber, saidrotation being sufiicient to cause said slag to form a uniform innerlayer over the inner surface of said metal so that said sulfur combineswith said slag in said inner layer thus removing at least a portion ofsaid sulfur impurities from said molten metal, and maintaining saidrotation until said metal solidifies so that the metal forms a tubularmember of increased quality;

14. A method of casting a tubular member having at least one internalflange comprising, the steps of pouring a predetermined quantity ofmolten metal into a tubular mold having a partition therein separatingthe interior thereof into a central chamber and a flange forming chamberconnected only by an annular passage formed between the outer peripheryof said partition and the inner surface of said mold, rotating said moldat a speed suificien-t to cause said molten metal to assume a uniformthickness over the inner surface of said mold, then placing a moltenmaterial having a melting point lower and a specific gravity less thanthat of said molten metal into said central chamber to force apredetermined amount of said molten material from said pressure cham- 20ber through said passage into said flange forming chamber and to act asa heat sink to eflect solidification of said metal in said centralchamber to proceed progressively from the outer surface inwardly to theinner surface to eliminate centerline cavities therein, and main- 12taining said rotation until said metal solidifies so that the metaladjacent said inner surface forms a tubular member of compact grainstructure and the metal in said flange forming chamber forms an internalflange on the tubular member.

References Cited by the Examiner UNITED STATES PATENTS 743,077 11/ 1903Hemptinne 2265 1,817,012 8/1931 Merle 2265 2,107,513 '2/ 193 8 Swoger2265 2,248,693 7/1941 Barscherer 22212 2,853,755 9/1958 Beyer 2220053,004,314 10/1961 Beyer 222005 3,077,013 2/1963 Dishman 22'200.53,181,210 4/1965 Montgomery 2265 3,201,829 8/1965 Cox et al. 2265FOREIGN PATENTS 568,929 7/ 1958 Belgium.

725,601 3/ 1955 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner.

R. S. ANNEAR, Assistant Examiner.

1. A METHOD OF CASTING A TUBULAR MEMBER HAVING AT LEAST ONE INTERNALFLANGE, COMPRISING THE STEPS OF POURING A PREDETERMINED QUANTITY OFMOLTEN METAL INTO A TUBULAR MOLD HAVING THE INTERIOR THEREOF SEPARATEDBY BAFFLES INTO PRESSURE AND FLANGE FORMING CHAMBERS INTERCONNECTED ONLYBY AN ANNULAR PASSAGE BETWEEN THE OUTER PERIPHERY OF THE BAFFLES ANDINNER SIDE WALLS OF SAID MOLD, ROTATING SAID MOLD ABOUT ITS AXIS AT ASPEED SUFFICIENT TO CAUSE SAID MOLTEN METAL TO ASSUME A UNIFORMTHICKNESS OVER THE INNER SIDE WALLS OF THE SAID MOLD, POURING APREDETERMINED VOLUME OF FLUID MATERIAL HAVING A SPECIFIC GRAVITY NOTGREATER THAN THAT OF SAID METAL IN SAID PRESSURE CHAMBER TO FORCE APREDETERMINED VOLUME OF SAID MOLTEN METAL FROM SAID PRESSURE CHAMBERTHROUGH SAID PASSAGE INTO SAID FLANGE FORMING CHAMBER, CORRELATING SAIDSPEED OF ROTATION AND THE VOLUME OF SAID MATERIAL SO THAT THE THICKNESSOF SAID METAL ON SAID INNER SURFACE IS AT LEAST EQUAL TO THE RADIALDIMENSION OF SAID PASSAGE, AND MAINTAINING SAID ROTATION UNTIL SAIDMETAL SOLIDIFICES SO THAT SAID METAL IN SAID PRESSURE CHAMBER FORMS ATUBULAR MEMBER HAVING AN INTEGRAL FLANGE THEREON IN EACH SAID FLANGEFORMING CHAMBER.